Synthesis of Two-Dimensional MoS2 and WS2 Films by Enclosed Chemical Vapor Transport Method below the Back-End-of-Line Temperature.

Two-dimensional materials hold great promise for postsilicon electronics, but their conventional high-temperature synthesis hinders integration with back-end-of-line processes. Here, we present an enclosed chemical vapor transport (ECVT) process for growing centimeter-scale uniform and continuous monolayer MoS2 and WS2 films at temperatures as low as 280 and 350 °C, respectively. The confined geometry of the ECVT system enhances the partial pressure of active molecular species, thereby reducing the energy barriers for both atomic nucleation and lateral migration of 2D materials on the substrate. The ECVT-synthesized MoS2 nanoflakes at 350 °C exhibit a single-domain size of ∼7 μm, an ultralow defect density of 1.14 × 1013 cm-2, a room-temperature mobility of ∼20 cm2 V-1 s-1, and an on/off ratio of ∼107 of the related transistors. This work may provide a viable pathway for BEOL-compatible 2D material integration.